Unknown sign-in provider
Social login callback received a provider that isSocialProvider does not recognize (oauth_unknown_provider).
Why this happens
Typo in the URL, stale bookmark, or custom/old provider slug. Distinct from This sign-in provider is not configured (known provider, missing credentials).
Diagnose and fix
1. Start again from the login page social buttons (do not hand-edit the callback URL).
2. Admin: enable only supported providers under Social login.
3. Confirm OAuth redirect URI points at the live app.
4. Use email/password if social is unavailable.